Adds flags for two omnibox experiments.

These need to be part of the EmbeddedSearch experiment.

BUG=311269, 304859, 315944, 315640

Review URL: https://codereview.chromium.org/64643002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233846 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233846